The object of the invention is a method defined in the preamble of claim 1 for detecting the home area in a mobile station, and a mobile station defined in the preamble of claim 9.
An aim is to establish that a mobile station is in its home area or in the area where it is mainly used in order to apply local call tariffs and local services.
From the patent publication EP 0 344 989 it is previously known a method to establish with the aid of a system identification number (SID) that a mobile station is in its home area. A mobile station according to the method has several identification numbers, of which it according to the SID selects one to be used. Thus the mobile station has several home areas, which it can detect with the aid of the SID it receives.
A problem of the known devices is that they are complex and expensive to realise.
The object of the invention is to obviate said disadvantages.
The method according to the invention is characterised by what is presented in claim 1. The mobile station according to the invention is characterised by what is presented in claim 9. Preferred embodiments of the invention are presented in the dependent claims.
The invention relates to a method for detecting the home area in a mobile station. According to the invention the home area is detected in the mobile station by comparing data received by the mobile station from base stations of the cellular network with predetermined home area data stored in the mobile station (LFP, Location FingerPrint).
In an application of the invention the home area data is determined based on at least part of the following data:
a) a mobile country code (MCC),
b) a mobile network code (MNC),
c) a location area code (LAC) and a related cell identity (CI) for all broadcasting channels (BCCH, Broadcast Control CHannel) which the mobile station is able to receive,
d) the received signal strengths (RSS) for all broadcasting channels BCCH,
e) the distance to all base stations (BTS, Base Transceiver Station) on the broadcasting channels BCCH, and
f) the timing advance (TA).
On the basis of the mobile station""s country code, mobile network code and location area code it is unanimously known where the receivable base stations are located. Preferably, averaging is used in determining the signal strengths, distances and timing advance, so that abrupt changes caused by the terrain should not interfere with the measurement result. The base stations from which this data is received are preferably selected so that only a few of the most adjacent stations are used to determine the data. Thus the location is advantageously determined as accurately as possible. Preferably, as many as possible of the previously listed data a) to f) are used in determining the location of the mobile station. Preferably, at least three of the data a) to f) are used. However, the invention is not limited to using exactly the data a) to f) listed previously. In various embodiments of the invention, only a part of the data a) to f) may be used, or other data and measurements may be used in addition to the data a) to f) to increase the accuracy of the determination.
In one application of the invention said comparison method comprises the following steps:
a) the home area data is compared with the data received by the mobile station;
b) the mobile station is deduced to be within the home area if the data received by the mobile station is within predetermined tolerances when compared with the home area data, and in the opposite case the mobile station is deduced to be outside the home area;
c) the deduced result is presented to the user; and
d) if the mobile station is within the home area, this is reported to the operator.
In one application of the invention said home area data is determined by storing the corresponding data in the mobile station when it is within the home area.
In one application of the invention said home area data is determined by deduction based on the cellular network structure and stored in the mobile station.
In one application of the invention there can be several home areas to be determined and identified.
In one application of the invention the home area to be determined is the basis for a certain service.
The mobile station according to the invention comprises a processor to define the mobile station""s home area data and to compare this data with the received data in order to detect the home area, a memory to store programs and home area data, an RF section to receive data and to send this data to a base station, a keyboard to activate definition of the home area, a display to present the home area comparison result, and a data bus for the data communication between the means.
An advantage of the invention is that the location of the mobile station is reliably detected. A further advantage is that no equipment changes are required due to the invention. Further, due to the invention the infrastructure of a cellular network does not have to participate when the location is determined. A service control point (SCP) in a cellular network controls call tariffs and services on the basis of the home location register (HLR). The database of the cellular network is situated in the home location register, which comprises permanent basic data of mobile subscribers registered in the network.